Overclocking A Dual Athlon-- Twice The Fun

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Like it says – Ryalnd Page

I’ve always wanted a dual CPU system to play with.

Until fairly recently, they’ve been reserved for servers and high-end workstations and equipped with an high-end price tag.

Recently, thanks to AMD, this has changed. AMD’s 760MPX chipset is the newest and affordable chipset supporting dual socket A processors in a SMP (Symmetrical Multi-Processing) configuration.

Motherboards utilizing this chipset have become semi-plentiful, with six choices currently on the market. They are for the most part relatively inexpensive. A Tyan S2466 refurbished can be had for less than $200 US online. Some other motherboards are a bit more, but hardly ever more than $300 US.

To save more even more money, you have the option to use cheaper CPUs in the board.

The only Athlon that officially supports SMP is the Athlon MP. However, it has been discovered that Athlon XPs will function properly in a dual-CPU setup as long as the L5 bridge on the processor is closed.

Older XPs come with the L5 uncut. Newer models have it laser cut and require it to be closed in order to work in a dual setup. This process is similar to unlocking the XP’s multiplier, but is easier because the pit of the laser incision doesn’t need to be filled.

People have many questions about this. For a good, succinct answer, see this thread in the overclockers forums.

The new, Morgan-cored Durons may also be used in SMP.

This all puts the price of a dual-Athlons well below that of a competing Intel Xeon system, and that’s all I have to say about the competitionā€¦ šŸ˜‰

I started to shop.

Motherboard

I read some reviews, and based on Firing Squad’s 760MPX motherboard roundup, I decided on the Gigabyte GA-7DPXDW due to its score.

Processors

I decided to pay a bit extra and got Athlon MP processors.

The differences between XPs and MPs are small:

  • MPs are ‘SMP Certified’ by AMD and are guaranteed to work in pairs.
  • MPs have the L5 bridges closed (duh!)
  • MPs have their multipliers unlocked. Yes, their L1s aren’t cut.

    These differences between an XP2000+ and an MP 2000+ cost me $50US per processor. Whether or not it’s worth it is up to you. For me, I was new to Athlon SMP and didn’t want to take the chance of getting an XP that wouldn’t run in SMP or wrongly closing an L5 bridge.


    Memory

    The Gigabyte board, like some 760MPX boards, requires registered DDR to work. This is for stability, which becomes more critical in SMP when you have DRAM feeding more than one CPU at a time. The recommended amount of memory is usually about 512mb per CPU so I went with 1024mb of Crucial PC2100 registered DDR in two 512mb sticks.

    Cooling

    This is a tricky issue. The 760MPX boards don’t necessarily follow the normal mechanical standard for socket A heatsinks. They don’t observe the same exclusion zones and some don’t have the 4-bolt holes around the socket, either.

    The Gigabyte has these holes, but I didn’t want to risk getting a pair of Alpha 8045s and have them not fit. I opted for the best, small HSF I could find: the Millenium Glaciator II.

    Storage

    One of this machine’s purposes was to be a file server. I wanted some redundancy and some speed so I wanted to run a level 5 RAID hard drive system. The Gigabyte, like a lot of newer motherboards, can come with an onboard Promise 2-channel ATA133 RAID controller. This can’t handle RAID 5, so that was out.

    I looked at U160 SCSI RAID controllers and drives, but found them too expensive. I decided I wanted an ATA RAID 5 capable controller and chose 3Ware Escalade 7410. This card uses a 64-bit PCI slot, has 4xATA100 channels, and is RAID 5 capable.

    For drives I used a quartet of Western Digital WD30000 30GB ATA100 7200rpm drives. This would yield me 90GB of storage after one drive was used for array parity. For information on RAID types go here.

    Other Hardware

    For graphics I used an old GeForce2 MX400 I had laying around. Graphics obviously weren’t important to me in this case but to the GA-7DPXDW’s credit, it has an AGP Pro slot for the high-end AGP cards.

    Sound is onboard but was disabled in BIOS. For LAN I used a 3Com 3C905B NIC. The GA-7DPXDW can come with an integrated NIC, ironically made by Intel, but mine didn’t. This is an attractive option as there are only three 32-bit PCI slots on this board.

    Saving a slot is an especially good idea for this one and saving one is a good idea, especially because the onboard USB for this motherboard does not work. That’s right.

    This board uses the old southbridge that AMD released with the USB controller non-functional. It has USB ports on it, but they are blocked by the custom I/O shield you put in the case when you install it.

    Something that redeems this, though, is the addition of a 4-port USB 2.0 card in the motherboard box. It does need a driver and OS installed to work, though, so if you use a USB keyboard and want to get into BIOS, forget it. Hook up a PS2 keyboard instead.

    If you are wondering why in the hell I used twin MP 2000+ CPUs for a file server that a Pentium 200 wouldn’t break a sweat doing, well, I like to fold proteins, too.

    AMD CPUs have untouchable non-SSE2 FPU performance, which is what Folding@Home relies on for its work. I figured this was a good excuse to put a pair of high-MHz AMDs to work for the cause.

    Building It

    I decided to cram all this into an Antec SX630 mid-tower case, and added an Antec TruePower 550-watt PSU. I hoped that the SX600 case would have enough airflow to cool the drives and the two hot-running Athlon CPUs.

    First, I got the motherboard populated with the CPUs, RAM and expansion cards:

    TMD

    Then I pulled the cards out of the motherboard (I just had them in there to make sure they’d fit) and stuffed it – literally – into the SX600. I wired everything up and got this:

    TMD

    Now it was time to get down to what we’re all about here: overclocking! The Gigabyte board has FSB adjustments in increments of 1 MHz. However, it has no voltage or multiplier adjustments. It does have memory timing tweaks.

    I started off by setting the RAM to the fastest timings. No problem there with the Crucial. Then I kicked up the FSB to 135mhz. It booted at 1690MHz. I ran Prime95 for two hours, no problem.

    Next came 137MHz FSB. Boot and torture test for the same amount of time at 1715MHz! I was happy already; these CPUs were damned fast and the RAID 5 was only a tiny bit slower than my old onboard HighPoint 2 drive RAID 0. I concluded this was because the Escalade used an onboard processor to do its striping algorithms and the HighPoint used host CPU cycles. The Escalade also had twice the bandwidth of the HighPoint because of the 64-bit PCI interface.

    That was it, brick wall for anything more than 1715Mhz/137MHz FSB. Anything higher than 137MHz on the front side bus would not boot. It would post, but then the Escalade would lose its RAID BIOS configuration and leave me sweating bullets until I rebooted at 133FSB and rebuilt the array with no data loss. Backing off memory timings didn’t help.

    Not a great overclock, but one that I can live with. I honestly didn’t expect a lot from a 760MPX board, though it looks like the Escalade is the culprit here. (Ed.note: SCSI and RAID controllers can be quite sensitive to FSB increases.)

    I’ve never overclocked a 64-bit PCI device before so I wonder if the double width of the bus makes it less tolerant to higher frequencies. If anybody knows why feel free to let me know.

    Here I am now with two Palominos chugging along at 1715MHz and giving the scores of Team 32 a good kick. The RAID is now home to my MP3 and movie collection.

    I’m happy with this.

    Overclocking dual Athlons: Twice the fun, twice as hard, less than half the overclock.

    For a lot more SMP information, look to the Overclockers.com SMP Forum.

    Ryland Page (aka in Forums as donny_paycheck).

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